In road vehicles it has become necessary and is in some countries required by law, that the vehicle has a brake on the fluid motors which drive the wheels or tracks. A coupling was therefore mounted around the shaft of the motor and supplied with fluid for action against a spring means through the outside of the housing of the motor. The control fluid supply from radially outside through the housing is however unconvenient and in addition the entering fluid is prevented or braked from radial inward flow at high speed of the revolving clutch or coupling. The control devices of the known art are therefore uneffective at high rotary speeds of the motor.
By the invention the control fluid is led through the centre of the rotor and enters the to be controlled members, like coupling, clutch, wheel, propeller or others or their control devices like small fluid motors or hydraulic or pneumatic cylinders or pistons radially from inside or in an axial direction or in an inclined direction therebetween. These directions of control flow of the invention make the control and remote control possible also at the very highest rotary revolutions of the rotor and members. At same time the unconvenience of fluid lines outside of the housing are prevented. The control fluid enters the motor from its axial end and thereby the control fluid lines radially of the housing are spared and radial eccessive space is prevented by the invention.